Evernia prunastri, or oakmoss, growing on a tree near town. Despite its name, oakmoss is not a moss or a plant of any kind, but a lichen.

Lichens are composite organisms made up of at least two separate species of fungus growing in partnership with one or more species of algae or Cyanobacteria. Lichens are real world “fusions” – distinct, unrelated organisms from different biological kingdoms combining to form unique life forms greater than the sum of their parts. The composite fungi provides protection while the algae supplies nutrients. Different combinations of fungi and algaes produce visually distinct types of lichens.

A true coastal species, H. heterophylla is regularly found along the Pacific from California’s North Coastal Redwood Forests through British Columbia. There are three species with a similar growth habit found west of the Cascades. H. heterophylla is characterized by having many dichotomous branches that occur at 45 degrees, forming a series of perpendicular branch patterns. Another species, H. imshaugii, rarely has a similar branching pattern but, when broken open, H. imshaugii has white interiors while H. heterophylla has black interiors. A third species, H. inactiva, also has a similar growth habit and dark interiors, but rarely exhibits perpendicular branches. While both H. imshaugii and H. inactiva are found east to Montana and Idaho, H. heterophylla is restricted to coastal forests only.